1. Field of the Invention
The present invention relates to an electrical module cover, an electrical module and an optical transceiver mounted in a cage of a host board (motherboard), and particularly, to its chassis structure.
2. Description of the Related Art
Pluggable optical transceivers which have become the main stream in recent years have, a tone end, insertable/removable optical connector cables having optical fibers that are transmission paths, and an optical transceiver (except for one end) is insertably/removably provided in a cage of a host board (motherboard) provided in an external device. This optical transceiver is used by mounting it in a cage of a motherboard.
As such an optical transceiver, an optical transceiver 121 as shown in FIGS. 1-3 comprises mainly a transceiver body 122, a transceiver chassis 123 in which is housed the transceiver body 122, and a metallic cover 124 fixed to the transceiver chassis 123. The transceiver body 122 has an optical transmitting/receiving module 126 fixed to a circuit substrate 125.
The optical transmitting/receiving module 126 is regulated in movement in directions other than a downward direction (−z direction), by the transceiver chassis 123, by fitting the optical transmitting/receiving module 126 into a holding portion 127 of the transceiver chassis 123. To regulate downward movement of the optical transmitting/receiving module 126, to the holding portion 127 is fixed a module holder 128 by engagement of engaging portions of a snap fastener or the like. The circuit substrate 125 is fixed to leg portions 129 of the transceiver chassis 123 by means of screws, respectively.
Using only the module holder 128 causes slight rattle in the engaging portions so that the optical transmitting/receiving module 126 cannot be firmly fixed to the transceiver chassis 123. The substantially cylindrical cover 124 is therefore used. This cover 124 is fixed to the transceiver chassis 123 by covering the transceiver chassis 123 with the cover 124 from the other end in the −x direction (by inserting the other end of the transceiver chassis 123 into the cover 124 in the +x direction).
In this case, the periphery of the transceiver chassis 123 except for its one end is covered with the cover 124, so that the optical transmitting/receiving module 126 is covered with the cover 124. Optical transceiver structure using such a cover 124 is common (see, e.g., U.S. Pat. No. 6,439,918).
In the optical transceiver 121, the height hc of the internal surface of the cover 124 is slightly greater than the height ht from the upper surface of the transceiver chassis 123 to the lowermost surface of the module holder 128 which holds the optical transmitting/receiving module 126 fitted into the holding portion 127 (hc>ht).
However, because of a slight difference between the height hc and ht, the optical transceiver 121 is difficult to be fabricated according to design, and in addition, because the cover 124 is metallic, it is difficult to be deformable.
For this reason, there is the problem that after the transceiver body 122 is housed, covering the transceiver chassis 123 with the cover 124 (inserting the transceiver chassis 123 into the cover 124) requires great force and is difficult, so that assembling is difficult. The optical transmitting/receiving module 126 can also be damaged.
On the other hand, if the height hc is too greater than the height ht, the optical transmitting/receiving module 126 cannot be firmly fixed by the transceiver chassis 123 and the cover 124, which may result in an optical-axis misalignment of the optical transmitting/receiving module 126. The above problems are also true of U.S. Pat. No. 6,439,918.